Covering aerofoils



June 7, 1932. w. HARPER, .JR

COVERING AEROFOILS Filed March l5, 1930 ...w ma Tw. ma VA IN.H

ATTORNEY Patented June 7, 1932 l UNITED STATES PATENT OFFICE WILLIAM HARPER, JR., OF PORT WASHINGTON, NEW YORK, ASSIGNOR TO SUPER- MARINE SYSTEMS,INC., OF NEW YORK, N. Y., A CORPORATION OF DELAWARE' COVERING .AEROFOILS Application led March 15, 1930. Serial No. 436,169.

This invention relates to attaching covers to aerofoils and other skeleton structures and has for its object to cover such bodies securely and much more rapidly than heretofore without tacking, sewing or other piecemeal methods.

In the preferred form of the invention I construct the edges of the skeleton structure in the form of channels having narrow longitudinal openings. The fabric cover is laid over the framework and the portions which lie over the openings in the channels are looped through and locked in the channels by means of reeds or the like which are threaded through from end to end.

The reed or otherlocking strip is threaded. throu h the channel by means of a needle or slider having a cam-sha ed head and an actuating handle which proJects through the narrow opening of the channel. To startthe covering operation, the edge of the fabric is looped into one end of the channel and the slider fitted inside such loop. Then, as the slider advances through the channel with the reed in tow, it plows over the looped fabric and cams succeeding portions into the channel and finally emerges at the other end where it is detached from the reed.

The invention will be described in connection with certain embodiments shown in the accompanying drzgving, in which:

Fig. 1 is a side elevation of the leading end of an airplane wing showing the method of attaching the cover;

2 is a similar view of the trailing end of the wing showing the slider at the end of its travel;

Fig. Sis a transverse section taken on the 1ine33ofFig.1;

Fig. 4 is a fragmentary plan view of a rib with the cover secured thereto;

Fig. 5 is a fragmentary section showing a modified form of rib;

Fig. 6 is a side view of the needle or slider showing oneA method of securing the reed thereto; and

Fig. 7 is a fragmentary section of a rib having a special device for bracing the channels.

The rib 1 shown in Figs. l and 2 is of the type commonly employed in fabricating airplane wings constructed 011 the stream-line principle, and is usually made of duralumin or other metal. wing a plurality of these ribs are arranged parallel to each other and are connected by transverse spars which extend through cutout portions 2 and are bolted or welded to the flanged edges 3 thereof.

In the form shown in Figs. l to 3 the rib itself is a single sheet of metal, while the curved channel-shaped edge 4 is formed of two opposite metal strips 5 having their intermediate portions 6 rolled to substantially semi-circular form and their outer edges 7 spun over and thus strengthened as best shown in Fig. 3. These strips are. bolted or welded to opposite sides of the 4rib l along the edges and form a curved channel of substantially circular cross-section having a narrow longitudinal opening 8 at the top.

In the preferred form of the invention the upper and lower channels are separate, but are nevertheless carried practically to the tip of the rib where they almost meet. In Fig. 1, for example, the two channels eX- tend almost to their natural terminus at the leading edge of the rib, and the tip of the rib itself is out out at 9, so as to leave just enough room to insert the locking reeds as hereinafter described. Likewise, in Fig. 2, the up- In building the skeleton per and lower channels are carried out as near y consequently a skeleton Wing having a. plurality of parallel ribs will have a like number of arallel channels into which I clamp the abric cover.

In covering the skeleton framework the usual fabric cover 10 is laid over the ribs,

and according to my invention the portions which lie over the longitudinal openings 8 are looped through and locked in the channels by means of locking strands 11 which are preferably circular in cross-section and only slightly narrower than the internal diameter of the channel 4. I prefer to use rattan reeds for this purpose since they are strong, tough and sufficiently flexible to be bent to any shape, and can readily be obtained in the desired sizes.

The reeds 1l are threaded through one end of each channel, and Fig. 1 shows a reed starting `into the channel at the leading end of the rib. In order to pull the reed through the channel I provide a needle or slider 12 having a rounded head 13 and an actuating handle 14 having a narrow shank 15 which projects through the longitudinal opening 8` in the channel. The slider 12 has a hole 16 in its rear end which may be threaded internally, as shown in Fig. 6, or otherwise formed to grip the end of the reed 11. lVhen a rattan reed is used the slider may be screwed over the end of the reed and adhesive material employed to strengthen the joint if desired.

In starting the covering operation it is only necessary to loop the edge of the fabric 10 into one end of the channel 4. For example, the edge of the fabric at the left-hand side of Fig. 1 is looped into the open'end of the channel, and .the slider 12 is inserted into the channel over the looped fabric. As the operator pulls the slider along with the reed fabric and cams succeeding portions of the fabric through the opening into the channel where it is locked securely by the reed, the slider finally emerging at the right-hand end in Fig. 2 where the reed is sawed olf to length and the slider detached.

It is desirable to thread the reeds through the channels one at a time so that as the fabric is locked in each succeeding rib it is drawntaut and stretched by the camming action of the reeds in locking. When the framework is completely covered I secure strips of fabric 17 to the cover directly over the channels. These strips may be glued or otherwise attached to the cover, and not only give the cover a smooth unbroken surface but also resist any tendency of the channels to spread apart. then treated with dope such as a nitrocellulose solution which shrinks it drum-tight.

An important advantage of the composite construction described above lies in the security of the lock whereby any tendency of the channels to separate is counteracted by the curvature of the channels. Regardless of thetension on the fabric cover 10, the only way it can pull out of its locked position in the channel is by pulling the iexible rod 11 out with it, and the traction created by the curvature of the channel is sufficient to prevent this even if the channel tends to spread at a certain point. Fig. 5 shows a modification of tlie inven- 11 in tow, the head 13 rides over the` The entire cover is tion in which the rib itselfv is made in the form of two similar sheets 18 which are bolted, welded or otherwise joined face to face, and have their edges rolled to form channels 4 similar to the channels described above. The method of covering is the same as in Figs. 1 to 4.

Fig. 7 shows another modification of the invention in which the ribs are formed with integral channeled edges as in Fig. 5, but in which special plates or braces 19 are cmployed to prevent any possibility of the channeled edges spreading under severe strain. These braces are in the form of angles secured to the ribs by bolts 20 and cut out or otherwise shaped to the contour of the ribs and channeled edges. The braces may be secured to the ribs at spaced intervals before the cover is attached.

It will be evident that the invention is capable of various other modifications and adaptations not specifically described but ineluded within lthe scope and spirit of the f invention as defined in the appended claims.

The invention claimed is: 1. A skeleton body for aerofoils having a channel-shaped edge with a narrow longi' tudinal opening, a pliable cover having a portion folded inside said channel, and-a strand threaded through the-fold of the cover to lock it in the channel.

2. A skeleton structure for aerofoils including a cuived channel provided with a continuous Vnarrow opening, a pliable cover for said structure having a portion looped through the opening in the channel, and a flexible rod in said channel threaded through the loop in the' cover to lock it in said channel.

3. A skeleton structure for aerofoils including a channel provided with a narrow longitudinal opening, a rattan reed disposed in and substantially filling said channel, and a'pliable cover for said structure having a' portion looped inside said opening and around said reed to lock said cover in Vsaid channel.

4. A skeleton structure for aerofoils hav'- ing a tubular edge open at the top and curved for a substantial portion of its length, a rattan reed disposed in and substantially filling said tubular edge, and a fabric cover for said structure having a portion looped aroundsaid reed to lock said cover in said tubular edge.

5. A skeleton structure for aerofoils constructed on the stream-line principle, comprising a tubular edge curved steeply for an appreciable portion of its length and having a narrow opening extending the full length ofthe tube, a lfabric cover for said structure having a portion looped through the openin in the tube, and a locking strand threaded t rough the loop in the fabric to lock it in said tube.

6. A skeleton structure for aerofoils comprising a pair of elongated metal strips each rolled to provide a groove adjacent one edge and secured together to provide an elongated channel having a narrow opening, and means to prevent the channel from spreading.

7. A skeleton structure for aerofoils comprising a pair of elongated metal strips each rolled to provide a groove adjacent one edge and secured together to provide an elongated channel having a narrow opening, and braces secured to the sides of said strlps to prevent said channel from spreading.

S. A device for threading rattan reeds and the like through a channel having a narrow longitudinal opening, comprising a slider having means for gripping the reed and an actuating handle having a narrow shank `adapted to track in the opening of said channel.

9. A skeleton structure oraerofoils comprising a pair of metal strips having grooves cooperating to form an elongated channel having a narrow longitudinal opening extending along the edge of the structure for securing a cover thereto.

l0. A skeleton structure for aerofoils comprising a pair of elongated metal strips rolled to provide substantially semi-circular portions having their outer edges spun over, and means for securing said strips together so that the semi-circular portions cooperate to form an elongated channel.

l1. A skeleton structure for aerofoils having a continuous channel-shaped edge with a narrow opening leading into the channel, a fabric cover for said structure having a portion looped through the opening into the channel, a locking strand threaded through the loop in the fabric to lock it in said channel, and a stri of material secured to the fabric cover directly over the channel reinforcing it against spreading.

Signed at New York in the county of New York and State of New York this 13th day of March A. D. 1930.

WILLIAM HARPER, JR. 

